Health Mailbox

Columnist Tara Parker-Pope answers readers' questions.

Updated Nov. 1, 2005 12:01 a.m. ET

Q: Your recent article about lung cancer in people who have never smoked begs the simple question: who never smoked what? One might assume you are referring to tobacco. May I remind you that marijuana is well into a third generation of mainstream population users.

—H.B.

A: It's true that marijuana smoke contains several of the same carcinogens as the tar from tobacco, but two recent reviews of the scientific research have concluded that smoking marijuana probably doesn't pose the same...